<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }
        section {
            display: flex;
            width: 60%;
            height: 80px;
            margin: 50px auto;
            background-color: pink;
        }
        section div:nth-child(1),section div:nth-child(3) {
            width: 80px;
            height: 80px;
            background-color: skyblue;
        }
        section div:nth-child(2) {
            flex:1;
            height: 80px;
            background-color: green;
        }

        .box {
            display: flex;
            width: 60%;
            height: 80px;
            margin: 50px auto;
            background-color: pink;
        }
        span {
            flex:1;
        }
        span:nth-child(2) {
            flex:2;
            background-color: blue;
        }

    </style>
</head>
<body>
    <section>
        <div>1</div>
        <div>2</div>
        <div>3</div>
    </section>
    <div class="box">
        <span>1</span>
        <span>2</span>
        <span>3</span>
    </div>
</body>
</html>